Sleeve bearing systems are well-known in the art and are used in a wide variety of machine systems to support rotating shafts. A typical sleeve bearing installation is a hydrodynamic system, in which a thin film of lubricating fluid, typically a petroleum-based or synthetic oil, forms a thin film or fluid “wedge” that provides support for a shaft rotating within the sleeve bearing. In a passively lubricated sleeve bearing system, a sump provided in the bearing housing contains the lubricating fluid (e.g., oil) for the bearing. One or more oil rings encircling the shaft are caused to rotate by the rotation of the shaft in the sleeve bearing. As the oil ring rotates, its lower portion dips into the oil contained in the sump. Continued rotation of the oil ring carries some of the lubricating oil to the top of the sleeve bearing, where it is deposited at or near the bearing/shaft interface. Thus, the oil ring provides the sleeve bearing with a continuous supply of lubricating fluid so long as the shaft is rotating.
While ring oiling systems of the type described above work well and are widely used, they only supply lubricant to the sleeve bearing when the shaft is rotating. The bearing is not supplied with lubricant during those times when the shaft is not rotating.